Skateboard

ABSTRACT

A body  11  that constitutes a skateboard is formed into a U shape with bases of a pair of plate-like legs  14, 15  being integrated, and end portions  17, 18  of the legs  14, 15  are relatively displaceable in a thickness direction by elasticity of the body  11 . The end portions  17, 18  of the legs  14, 15  are coupled by a coupling member  19 . One wheel  12  is provided on a lower surface of an integral portion  16  at the base ends, and the other wheel  13  is provided on a lower surface of the coupling member  19 . The step board  41  is placed between the end portions  17, 18  of the legs  14, 15 , and has contact portions  46, 53  that come into contact with the legs  14, 15  by following displacement of the end portions  17, 18  of the legs  14, 15  in the thickness direction.

FIELD OF THE INVENTION

The present invention relates to a skateboard, and more particularly to a skateboard including casters swingable around an inclined pivot as traveling wheels.

BACKGROUND OF THE INVENTION

As such a skateboard, WO2007/127554 describes a skateboard having a one piece body made of a material twistable around a front-back axis. This body includes a pair of front and rear foot support areas, and a central section between the foot support areas. The central section is narrower than the foot support regions so as to twist the body.

With such a configuration, a user on a traveling skateboard can adjust forces applied to the body from the feet on the foot support regions to twist the body as described above. When the body is twisted, a front caster provided on a lower surface of a front foot support area and a rear caster provided on a lower surface of a rear foot support area are swingable around an inclined central axis, and thus turn in opposite lateral directions. This causes the skateboard to travel in a serpentine manner, and a component of force at that time generates forward propulsion. Thus, the skateboard travels by itself simply by the user twisting the body without additionally pushing off on the ground.

DISCLOSURE OF THE INVENTION

However, in order to sufficiently turn the front and rear casters in the opposite lateral directions, the body needs to be significantly twisted. Thus, large forces need to be applied from the feet to the body. Thus, the skateboard does not have sufficient operability.

Therefore, the present invention has an object to solve such a problem and allow casters having an inclined central axis to be sufficiently laterally swingable even if a user on a skateboard applies small forces.

To achieve this object, the present invention provides a skateboard including: a body; wheels at front and rear of a lower surface of the body; a coupling member; and a step board, wherein the wheels are constituted by swingable casters having an inclined pivot, the body is formed into a U shape with bases of a pair of plate-like legs being integrated, end portions of the pair of legs are relatively displaceable in a thickness direction thereof by elasticity of the body, the end portions of the pair of legs are coupled by the coupling member so as to be displaceable in the thickness direction, one of the swingable casters is provided on a lower surface of the integrated bases of the pair of legs, the other of the swingable casters is provided on a lower surface of the coupling member, and the step board is placed between the end portions of the pair of legs and has a contact portion that comes into contact with the legs by following displacement of the end portions of the legs in the thickness direction.

According to the present invention, the body is constituted by a U-shaped member with the bases of the pair of plate-like legs being integrated, the end portions of the pair of legs are coupled by the coupling member so as to be displaceable in the thickness direction by the elasticity of the body, and the swingable caster is provided on the lower surface of the coupling member. Thus, when the end portions of the pair of legs are displaced in the thickness direction, the coupling member is inclined according to the displacement of the legs. Then, the caster provided on the coupling member swings around the inclined pivot, and is thus significantly turned according to an inclination of the coupling member.

Specifically, according to the present invention, the end portions of the pair of plate-like legs that constitute the U-shaped body are relatively deformed with small forces in the thickness direction by the elasticity of the body, and thus the coupling member can be inclined between the legs, and the inclination allows the caster to be sufficiently turned.

Further, according to the present invention, the step board having the contact portion that comes into contact with the pair of legs according to the displacement of the end portions of the legs in the thickness direction is placed between the end portions of the legs. Thus, in positions of the end portions of the legs, a complex configuration is provided in which the pair of legs and the coupling member are provided and the legs are coupled by the coupling member, and a complex operation based on the configuration is performed. Nevertheless, an operator can stably place the foot on the step board, and can easily operate the skateboard.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a plan view of an embodiment of a skateboard according to the present invention;

FIG. 1B is an elevation view of the skateboard;

FIG. 2 shows the skateboard seen from the back;

FIG. 3 shows the skateboard seen from the back obliquely;

FIG. 4 is an exploded view of a rear portion of the skateboard;

FIG. 5 is a sectional view of a mounting state of a step board of the skateboard;

FIG. 6A is a plan view of a body that constitutes the skateboard according to the present invention;

FIG. 6B shows a state of displacement of legs by elasticity of the body;

FIG. 7 shows a configuration and an operation of the body and a coupling member that constitute the skateboard according to the present invention;

FIG. 8A shows an operation state of the skateboard;

FIG. 8B shows a configuration without a coupling member for comparison with FIG. 8A;

FIG. 9A is a plan view showing an operation state of the skateboard;

FIG. 9B shows the skateboard in FIG. 9A seen from the back;

FIG. 9C is a plan view showing another operation state of the skateboard;

FIG. 9D shows the skateboard in FIG. 9C seen from the back;

FIG. 10A is a plan view showing another embodiment of a skateboard according to the present invention;

FIG. 10B is an elevation view of the skateboard in FIG. 10A;

FIG. 11 is a sectional view showing a mounting state of a step board of the skateboard in FIG. 10A;

FIG. 12 shows the skateboard in FIG. 10A seen from the back;

FIG. 13 shows a step board in FIG. 12;

FIG. 14A shows an exemplified structure of the step board;

FIG. 14B show an operation of the step board in FIG. 14A;

FIG. 15 shows a variant of the structure of the step board;

FIG. 16 is an enlarged view of essential portions in FIG. 15;

FIG. 17 shows the essential portions of the skateboard in FIG. 15 seen from the back;

FIG. 18A is a plan view showing a structure of essential portions of a further embodiment of a skateboard according to the present invention;

FIG. 18B shows portions in FIG. 18A seen from the back;

FIG. 19A is a perspective view showing a structure of essential portions of a further embodiment of a skateboard according to the present invention;

FIG. 19B is a plan view of portions in FIG. 19A; and

FIG. 19C shows the portions in FIG. 19B seen from the back.

DESCRIPTION OF THE EMBODIMENTS

As shown in FIGS. 1A and 1B, a skateboard according to an embodiment of the present invention includes a plate-like body 11 and a pair of front and rear wheels 12, 13 on a lower surface of the body 11. A plurality of wheels may be provided on at least one of front and rear sides.

The body 11 has a U shape on plan view, and includes a pair of legs 14, 15 that form the U shape and have a predetermined width. Reference numeral 16 denotes an integral portion at which bases of the legs 14, 15 are integrated, which forms a curved portion of the U shape. Reference numerals 17 and 18 denote end portions of the legs 14, 15. The body 11 may include the integral portion 16 at which the bases of the pair of legs 14, 15 are integrated, and the end portions 17, 18 of the legs 14, spaced apart, and thus need not have an exact U shape. For example, the body 11 may have a V shape or other shapes, and such shapes are generally referred to as “U shape” in the present invention.

In the body 11, the end portions 17, 18 of the pair of legs 14, 15 are relatively displaceable in a thickness direction by elasticity of the body 11 as described later in detail. The body 11 may be made of plate-like synthetic resin so as to be elastically displaceable. Alternatively, the body 11 may be made of wood, light metal, composite materials, or the like.

A coupling member 19 is placed between inner edges of the legs 14, 15 in the end portions 17, 18. In an example in FIGS. 1A and 1B, the coupling member 19 is formed of a plate material, and has one and the other ends coupled to the inner edges of the legs 14, 15 via hinges 20, 20. The coupling member 19 may be made of the same material as or a different material from that of the body 11.

Front and rear sides of the skateboard in FIGS. 1A and 1B may be determined so that, for example, the integral portion 16 is on the front side and the end portions 17, 18 of the legs 14, 15 are on the rear side. On the skateboard, the wheel 12 as a front wheel is provided on a lower surface of the integral portion 16 on the front side, and the wheel 13 as a rear wheel is provided on a lower surface of the coupling member 19 on the rear side as shown in FIGS. 1A, 1B and 2.

As shown in FIG. 1A, the wheels 12, 13 are constituted by swingable casters. Reference numerals 23 and 24 denote pivots of the wheels 12, 13. The pivots 23, 24 are inclined forward so that upper sides are located on a more front side of the skateboard. When the skateboard is placed with the wheels 12, 13 in contact with the ground or a floor, the inclined pivots 23, 24 allow the wheels 12, 13 to roll in a longitudinal direction of the skateboard on the rear side of the pivots 23, 24 as shown based on the weight of the skateboard.

As shown in FIGS. 1A to 5, a step board 41 is placed between upper surfaces of the end portions 17, 18 of the legs 14, 15. Like the body 11, the step board 41 can be made of synthetic resin, wood, light metal, composite materials, or the like, and also formed of, for example, a plate member elongated in a width direction of the body 11 as shown. On a lower portion of the step board 41, a pair of brackets 42, 42 is formed integrally with the step board 41 so as to be spaced apart from each other in the longitudinal direction of the body 11 and protrude downward from a lower surface of the step board 41.

The coupling member 19 includes a mounting shaft 43. The mounting shaft 43 is placed horizontally in the longitudinal direction, that is, a front-back direction of the body 11. In the shown example, a base portion of the mounting shaft 43 is mounted to the coupling member 19, and an end portion thereof protrudes from the coupling member 19 toward a rear end of the body 11. The protruding end portion of the mounting shaft 43 extends through the brackets 42, 42. The brackets 42, 42 have through holes 44, 44 through which the mounting shaft 43 extends. The through holes 44, 44 are formed as slots in a displacement direction of the end portions 17, 18 of the legs 14, 15, that is, in a thickness direction of the legs 14, 15. A separation preventing member 45 such as a nut for preventing the step board 41 from being separated from the mounting shaft 43 is fitted to a portion of the mounting shaft 43 protruding from the rear bracket 42. Thus, in the shown example, the step board 41 is located immediately above the rear wheel 13 when the rear wheel 13 can roll in the longitudinal direction of the skateboard on the rear side of the pivot 24 as described above.

Contact surfaces 47, 47 for supporting a flat lower surface 46 as a contact portion of the step board 41 are formed on upper surfaces of the end portions 17, 18 of the legs 14, 15 of the body 11. Each contact surface 47 has a curved surface that can come into linear contact with the lower surface 46 of the step board 41 in the longitudinal direction, that is, the front-back direction of the body 11. Such a curved surface is, for example, a cylindrical surface having a central axis in the longitudinal direction of the body 11. To form the contact surfaces 47, 47, protrusions 48, 48 are formed on the upper surfaces of the end portions 17, 18 of the legs 14, 15 integrally with or separately from the legs 14, 15. Alternatively, the upper surfaces of the legs 14, 15 may be formed to be flat, and a protrusion 48 having a curved contact surface 47 may be formed on the step board 41. Further, protrusions 48 each having a curved contact surface 47 may be formed on both the legs 14, 15 and the step board 41.

As shown in FIG. 1A, an operator of the skateboard places one foot 25 on the integral portion 16 corresponding to the front wheel 12, and the other foot 26 on the step board 41 corresponding to the rear wheel 13, and then can operate the skateboard.

An operation of the skateboard will be described. Only the plate-like body 11 of the skateboard in FIGS. 1A and 1B is shown in FIGS. 6A and 6B. As shown, in the body 11, the legs 14, 15 are cantilevered from the integral portion 16, and the end portions 17, 18 of the legs 14, can be relatively displaceable in the thickness direction by elasticity of the body 11. Specifically, a surface of the body 11 is horizontally placed, and for example, the right leg 14 can be vertically displaced with respect to the left leg 15, and vice versa.

FIG. 7 shows a state where the coupling member 19 is mounted to the body 11 in FIGS. 6A and 6B via the hinges 20, 20. If the end portions 17, 18 of the legs 14, 15 of the body 11 are relatively displaced in the thickness direction, the leg 14 and the coupling member 19 are bent at one hinge 20, and the leg 15 and the coupling member 19 are bent at the other hinge 20. Thus, the coupling member 19 is inclined in a width direction, that is, a lateral direction of the skateboard. When the coupling member 19 is inclined, the legs 14, 15 are then slightly elastically deformed to narrow a space between the end portions 17, 18.

FIG. 8A shows such a bent state seen from a rear portion of the skateboard. As shown in FIG. 1A, the swingable caster that constitutes the rear wheel 13 has the pivot 24 inclined forward of the skateboard on the more front side. Thus, when the coupling member 19 is inclined in the width direction of the skateboard, the caster swings along therewith. For example, as shown in FIG. 9B, when the legs 14, 15 are displaced in the thickness direction so that the end portion 18 of the left leg 15 is lower than the end portion 17 of the right leg 14, the plate-like coupling member 19 is inclined diagonally right up. Then, the swingable caster that constitutes the wheel 13 turns to the right as shown. Specifically, the caster swings so as to be able to travel forward to the left. When the coupling member 19 is inclined diagonally left up to the contrary, the swingable caster that constitutes the wheel 13 turns to the left, although not shown. Specifically, the caster swings so as to be able to travel forward to the right.

The legs 14, 15 can be displaced by elasticity of the body 11 by the operator operating the step board 41 using the foot on the step board 41. Specifically, if the operator places the weight on a side of the step board 41 corresponding to one of the legs 14, 15, the one leg on which the weight is placed is displaced downward from the other leg. At this time, the step board 41 follows relative displacement of the legs 14, 15 in the thickness direction, and is inclined around the mounting shaft 43. Then, the step board 41 is loosely coupled to the mounting shaft 43 via the through holes 44 constituted by the slots. Also, the contact surfaces 47 of the protrusions 48 on the legs 14, 15 have the curved surfaces such as cylindrical surfaces having a central axis in the longitudinal direction of the body 11. Thus, even if the legs 14, 15 are relatively displaced in the thickness direction, the step board 41 can always follow the displacement in contact with the contact surfaces 47.

For a relationship between the mounting shaft 43, the step board 41, and the contact surfaces 47, the lower surface 46 of the step board 41 may be always in contact with the contact surfaces 47 irrespective of a relative displacement amount of the legs 14, 15 in the thickness direction and an inclination of the step board 41 according to the displacement amount. For this purpose, as described above, it is effective that the through holes 44 in the brackets 42 of the step board 41 are formed as slots in the thickness direction of the legs 14, 15, and the contact surface 47 is the cylindrical surface having the central axis in the longitudinal direction of the body 11. Other configurations may be used.

As shown in FIGS. 1A and 1B, when the body 11 is horizontal, and the end portions 17, 18 of the legs 14, are not relatively displaced in the thickness direction, the front and rear wheels 12, 13 constituted by the swingable casters having the inclined pivots 23, 24 are in positions to travel straight ahead. FIG. 2 shows a traveling state of the skateboard when the operator places the foot 26 on the rear step board 41 of the skateboard to keep the body 11 in the horizontal position, and the end portions 17, 18 of the legs 14, 15 are not relatively displaced in the thickness direction.

In this state, for example, as shown in FIG. 8A, the body 11 is elastically deformed so that the end portion 17 of the right leg 14 is higher than the end portion 18 of the left leg 15, the coupling member 19 is inclined diagonally right up as shown, and along therewith, the pivot 24 of the swingable caster that constitutes the rear wheel 13 is inclined to the left. Then, the swingable caster that constitutes the wheel 13 turns to the right. To control heights of the end portions 17, 18 of the legs 14, 15, the operator placing the foot 26 on the step board 41 as shown in FIG. 2 applies forces, that is, places the weight on a toe side or a heel side to press the end portion of the corresponding leg. Thus, the end portion is placed in a lower position than the opposite end portion.

At this time, the coupling member 19 is inclined between the inner edges of the left and right legs 14, 15 using the hinges 20, 20. Thus, the coupling member 19 can be significantly inclined depending on a difference in height between the end portions 17, 18 of the legs 14, 15, thereby causing the wheel 13 with a caster structure to swing with a large angle. At this time, in the shown example, the step board 41 is placed immediately above the rear wheel 13 as described above, thereby causing the wheel 13 to swing with a smaller force than when the step board 41 is placed in a different place. As described later, of course, a configuration may be used in which the step board 41 is placed in a position other than immediately above the rear wheel 13.

Specifically, as shown in FIG. 8B, when a body 11A is formed of a solid plate without left and right legs, a pivot 24A of a wheel 13 is inclined perpendicularly to an inclination direction of the body 11A. In contrast to this, in the case where the legs 14, 15 having a predetermined width of the body 11 are coupled at the inner edges by the coupling member 19 using the hinges 20, when outer edges of the legs 14, 15 are aligned with plate edges 31, 32 of the body 11A in inclination of the body 11A having the solid plate structure, the coupling member 19 is inclined with a larger angle than that of the body 11A. This is because the end portions 17, 18 of the plate-like legs 14, 15 are relatively displaced in the thickness direction, and thus a difference in height between the inner edges of the legs 14, 15 is substantially equal to a difference in height between the outer edges. Thus, in this case, as shown in FIG. 8A, the pivot 24 of the wheel 13 is inclined with a larger angle than that of the pivot 24A of the solid plate body 11A shown by a phantom line. Thus, as compared to the case of the solid plate body 11A, the wheel 13 constituted by the swingable caster can be significantly turned, thereby allowing the skateboard to be turned with a small radius.

At this time, the step board 41 is placed immediately above the rear wheel 13 as in the shown example to allow the wheel 13 to be turned with a small force, thereby allowing the skateboard to be turned with extremely high operability.

As shown in FIGS. 9C and 9D, during traveling of the skateboard, for example, a rightward force in the horizontal direction can be applied to the body 11 from the foot on the front of the body 11, and a leftward force in the horizontal direction can be applied to the body 11 from the foot on the rear of the body 11 without generating a difference in height between the left and right end portions 17, 18 of the legs 14, 15. Then, with the forces, the front wheel 12 constituted by the swingable caster swings to the left and is about to travel rightward as shown, and similarly, the rear wheel 13 constituted by the swingable caster swings to the right and is about to travel leftward.

Thus, the body 11 turns to the right. If the forces applied to the body 11 from the front and rear feet are reversed during the turn, the front and rear wheels 12, 13 swing in the directions opposite to the above. Further, an operation of reversing the forces applied to the body 11 from the front and rear feet is repeated to cause the body 11, that is, the skateboard to travel in a serpentine manner with a wave-shaped path 21. At this time, as shown in FIGS. 1A and 1B, the front and rear wheels 12, 13 are constituted by the swingable casters, and the pivots 23, 24 are inclined forward on the more front side of the skateboard. Thus, the swinging causes a forward component of force to be applied to the wheels 12, 13. Thus, the skateboard can keep traveling without pushing off on the ground.

FIGS. 9A and 9B show a state where a difference in height is generated between the end portions 17, 18 of the left and right legs 14, 15 during traveling of the skateboard according to the present invention. Thus, even when a similar operation to those in FIGS. 9C and 9D is operated, the rear wheel 13 can be significantly swung as compared to the case in FIGS. 9C and 9D. This can increase a forward component of force applied to the rear wheel 13 and generate larger traveling propulsion as compared to the case in FIGS. 9C and 9D. A traveling path 22 has a smaller wave shape than in FIGS. 9C and 9D.

In the operation in FIGS. 9C and 9D, if the wheel 13 is to be significantly swung as in FIGS. 9A and 9B, the operator has to apply considerable forces from the feet to the body 11. However, as shown in FIGS. 9A and 9B, when the difference in height is generated between the end portions 17, 18 of the left and right legs 14, 15 to incline the coupling member 19 and swing the wheel 13, a desired operation can be performed with a relatively small force without applying the large force.

The operation at this time may be performed by the foot on the step board 41. Thus, in the positions of the end portions 17, 18 of the legs 14, 15, a complex configuration is provided in which the pair of legs 14, 15 and the coupling member 19 are provided and the legs 14, 15 are coupled by the coupling member 19, and a complex operation based on the configuration is performed. Nevertheless, the operator can stably place the foot on the step board 41, and can easily operate the skateboard.

FIGS. 10A to 13 show a skateboard according to another embodiment of the present invention. The skateboard of this embodiment is different from the skateboard in FIGS. 1A to 9D in that the step board 41 is placed immediately above the coupling member 19. Specifically, as shown in FIG. 11 in detail, a body of a step board 41 and a pair of brackets 42, 42 are placed over a coupling member 19, and a bolt as a horizontal mounting shaft 43 that extends through a through hole 44 in each bracket 42 is threaded into front and rear end surfaces of the coupling member 19 in a front-back direction of the skateboard. Thus, the step board 41 is placed immediately above the coupling member. In the skateboard in FIGS. 10A to 13, the step board 41 has a large width, that is, the step board 41 has a relatively large size in the front-back direction of the skateboard. Thus, the step board 41 is placed immediately above the coupling member 19, and also placed above a rear wheel 13.

Specifically, as shown in FIG. 11, the pair of brackets 42, 42 of the step board 41 hold the coupling member 19 from front and rear. Thus, the step board 41 can be made more compact than that in FIG. 5. Also, the step board 41 has a large width and is also placed above the rear wheel 13, thereby allowing the wheel 13 to be turned with a small force as described above for turning the skateboard during traveling.

The step board 41 of the skateboard in FIGS. 10A to 13 has skirts 52 integrally formed to fill gaps between the step board 41 and legs 14, 15 of a body 11, particularly, gaps formed at ends in a width direction of the skateboard. More specifically, the skirts 52 are formed to protrude downward from the ends of the step board 41 in the width direction of the skateboard so as to fill the gaps. Also, the skirts 52 are configured so as not to abut against the legs 14, 15 even when end portions 17, 18 of the legs 14, 15 are relatively displaced in a thickness direction. This can effectively prevent an operator's finger from being caught in the gap between the step board 41 and the legs 14, 15.

FIGS. 14A and 14B show an exemplified structure of the step board 41. In the embodiment in FIGS. 1A to 9D, for example, the flat lower surface 46 is formed as the contact portion of the step board 41, and the lower surface 46 comes into contact with the contact surfaces 47 of the protrusions 48 of the legs 14, 15. In the embodiment shown in FIGS. 1A to 9D, the through holes 44 through which the mounting shaft 43 extends are the slots in the direction of elastic deformation of the end portions 17, 18 of the legs 14, 15. Thus, the step board 41 is loosely displaceable with respect to the mounting shaft 43 and the legs 14, 15. Thus, for example, when the skateboard is not used, the step board 41 can slightly move with respect to the legs 14, 15, and thus lacks stability. Also, abnormal noise is produced every time the lower surface 46 of the step board 41 collides with the contact surfaces 47 of the legs 14, 15.

To address such a situation, in the step board 41 in FIG. 14, contact portions that come into contact with the legs 14, 15 are configured as elastic tongues 53. When the step board 41 is made of, for example, synthetic resin, the elastic tongues 53 may be formed integrally with a body of the step board 41, and formed of bent leaf springs cantilevered from the body. In the shown example, a pair of elastic tongues 53 is formed for each protrusion 48 of the legs 14, 15. When the step board 41 is mounted to the coupling member 19 by the mounting shaft 43, an end portion of each elastic tongue 53 is pressed by the protrusion 48, thus each elastic tongue 53 is elastically deformed and is set while being elastically deformed by preloading.

At this time, the end portion of each elastic tongue 53 presses the protrusion 48 of the step board 41, and thus the step board 41 is lifted from the legs 14, 15 by reaction, and stabilized with a bottom edge of the through hole 44 being pressed against the mounting shaft 43. Thus, the step board 41 does not freely move with respect to the mounting shaft 43 and the legs 14, 15, and is thus stabilized, and collision between members can be prevented.

In the shown example, the pair of elastic tongues 53, 53 is provided for each protrusion 48 of the legs 14, 15, but any configuration may be used. For example, a single elastic tongue 53 may be provided for each protrusion 48. Instead of the elastic tongue 53, the protrusions 48, that is, the legs 14, 15 may be formed of elastic bodies that can be pressed. The elasticity bodies may be formed integrally with the step board 41 as described above, or separately formed. In the shown example, the size of the elastic tongue 53 in the front-back direction of the skateboard, that is, the size of the elastic tongue 53 in a direction perpendicular to the sheet surface of FIG. 14 may be appropriately determined.

FIGS. 15 to 17 show a different exemplified configuration in which the step board 41 is kept stable to prevent collision between members. In this configuration, a torsion coil spring 54 is externally fitted on the mounting shaft 43, one and the other ends 55, 55 of a wire that forms the torsion coil spring 54 protrude upward from the mounting shaft 43, and the pair of ends 55, 55 hold a stopper 56 formed on the coupling member 19 with torsion elasticity of the spring. Specifically, the torsion coil spring 54 is stably kept by the pair of ends 55, 55 elastically holding the stopper 56. With such a configuration, a space is formed between the pair of ends 55, 55, and a projection 57 that can fit in the space is formed integrally with the step board 41.

In this configuration, for example, when the skateboard is not used, the projection 57 of the step board 41 is regulated by the torsion coil spring 54 to prevent the step board 41 from freely oscillating or turning around the mounting shaft 43. This advantageously allows the step board 41 having the contact portion lifted from the contact surfaces 47, 47 of the legs 14, to be stably kept with respect to the legs 14, 15, and prevents collision between the members.

When the legs 14, 15 are relatively displaced in the thickness direction of the skateboard by the step board 41 during the operation of the skateboard, the step board 41 may be strongly turned around the mounting shaft 43 against a spring force of the torsion coil spring 54.

FIGS. 18A and 18B show a skateboard of a further embodiment of the present invention. In the skateboard in FIGS. 1A to 17, the legs 14, 15 of the body 11 and the coupling member 19 are coupled by the hinges 20, 20. In the skateboard in FIGS. 18A and 18B, legs 14, 15 of a body 11 and a coupling member 19 are coupled by ball joints 33. The ball joints 33 are configured so that balls 34, 34 formed on one of the legs 14, 15 and the coupling member 19 fit in recesses 35, 35 formed in the other. In the shown example, the balls 34, 34 are formed on the coupling member 19, and the recesses 35, 35 are formed in the legs 14, 15.

When the body 11 is made of synthetic resin, the balls 34, 34 are firmly pressed into the recesses 35, 35 to elastically deform the resin around the recesses 35, 35, and thus can be fitted into the recesses 35, 35. Although not shown, protruding stoppers are preferably formed on inner surfaces of the recesses 35, 35 so that the balls 34, 34 can be easily fitted into the recesses 35, 35, but are hard to be removed from the recesses 35, 35. Such stoppers may be protrusions having a gentle inclination in a fitting direction of the balls 34, 34 but having a steep inclination in a removing direction. In this case, the balls may be made of any material, but for example, the coupling member 19 and the balls 34, 34 are preferably made of the same resin as the body 11.

As such, when the legs 14, 15 and the coupling member 19 are coupled by the ball joints 33, a coupling portion may have increased flexibility as compared to the coupling structure using the hinges 20, 20 described above. Thus, the coupling portion can address a case where the legs 14, 15 of the body 11 are displaced in the thickness direction, and also a case where the legs 14, of the body 11 are relatively displaced in other complex directions.

FIGS. 19A, 19B and 19C show a skateboard according to a further embodiment of the present invention. A body 11 including legs 14, 15 is made of synthetic resin, and a coupling member 19 is made of the same synthetic resin as the legs 14, 15 with a thickness equal to or different from that of the legs 14, 15, and formed integrally with the legs 14, 15. Thin portions 37, 37 along inner edges of the legs 14, 15 are formed at boundaries between the legs 14, 15 and the coupling member 19. The thin portions 37, 37 are formed to be smaller in a thickness direction than the legs 14, 15 and the coupling member 19. The thin portions 37, 37 are formed, and thus grooves 38 along the inner edges of the legs 14, 15 are formed at the boundaries between the legs 14, 15 and the coupling member 19 on both front and back surfaces.

With such a configuration, the thin portions 37 having the grooves 38 formed on both the upper and lower surfaces of the legs 14, 15 and the coupling member 19 may have the same function as the hinges 20 described above. Thus, similarly, the end portions 17, 18 of the legs 14, 15 can be relatively displaced in the thickness direction. In this case, the legs 14, 15 and the coupling member 19 are repeatedly elastically deformed to be bent, and thus the body 11 and the coupling member 19 including the thin portions 37 need to be made of a synthetic resin material so as to resist such repeated deformation. In this case, the thin portion 37 is made of elastically deformable resin, and thus can address a case where the legs 14, 15 are displaced in the thickness direction by elasticity of the body 11, and also a case where the legs 14, 15 are displaced in other complex directions. Further, with this configuration, the legs 14, 15 and the coupling member 19 are integrally formed via the thin portion 37, thereby reducing the number of components as compared to the case where the legs 14, 15 and the coupling member 19 are separately formed.

According to the present invention, the coupling structure between the legs 14, 15 and the coupling member 19 is not limited to the example described above, but any configuration may be used as long as the legs 14, 15 and the coupling member 19 are coupled so that the legs 14, are displaceable in the thickness direction by the elasticity of the body 11. 

What is claimed is:
 1. A skateboard comprising: a body; wheels at front and rear of a lower surface of the body; a coupling member; and a step board, wherein the wheels are constituted by swingable casters having an inclined pivot, the body is formed into a U shape with bases of a pair of plate-like legs being integrated, end portions of the pair of legs are relatively displaceable in a thickness direction thereof by elasticity of the body, the end portions of the pair of legs are coupled by the coupling member so as to be displaceable in the thickness direction, one of the swingable casters is provided on a lower surface of the integrated bases of the pair of legs, the other of the swingable casters is provided on a lower surface of the coupling member, and the step board is placed between the end portions of the pair of legs and has a contact portion that comes into contact with the legs by following displacement of the end portions of the legs in the thickness direction.
 2. The skateboard according to claim 1, wherein the step board is mounted to the coupling member.
 3. The skateboard according to claim 1, wherein the step board is pivotable around an axis in a front-back direction of the skateboard, the end portions of the pair of legs have contact surfaces with which the contact portion of the step board comes into contact by following displacement of the end portions of the legs in the thickness direction, and at least one of the contact surfaces of the legs and the contact portion of the step board has a curved surface.
 4. The skateboard according to claim 1, wherein the coupling member and one and the other legs are coupled by hinges.
 5. The skateboard according to claim 3, wherein the contact portion of the step board is pressed against the contact surfaces of the legs by spring elasticity.
 6. The skateboard according to claim 3, further comprising a holding member for holding the step board in a certain position when the contact portion of the step board moves from the contact surfaces of the legs. 